Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

589
FXUS63 KLOT 240726
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
226 AM CDT Sun May 24 2026

.KEY MESSAGES...

- Showers and thunderstorms are expected through midday, with
  highest chances along and east of I-55. Primary concern is
  downpours leading to ponding in poor drainage areas.

- Above normal temperatures through the early part of the week,
  though cooler near Lake Michigan.

&&

.DISCUSSION...
Issued at 226 AM CDT Sun May 24 2026

Festering showers continue to bubble up west of the forecast
area, closer to a surface front analyzed along or just west of
the Mississippi River. With weaker forcing, coverage is a little
lacking leading to more isolated to localized clusters
developing. A few lightning strikes may be possible, but with
limited instability, confidence low. Some of these showers may
continue into the area west of the Fox Valley through the next
couple of hours.

The previously mentioned front is expected to sweep across the
area through the early morning, exiting to the east around
midday. Coverage of showers along and ahead of the front is
expected to increase closer to daybreak along the better
forcing with the arrival of a mid level wave. Southerly winds
will advect in an almost tropical air mass with precipitable
water amounts north of 1.50 inches. With slow storm motions
(around 20 mph or less) nearly parallel to the front, the
primary threat is for downpours and even localized torrential
rainfall. Widespread flash flooding is not expected, but with
intense rain rates (locally greater than an inch per hour) and
possible training there is a chance that there could be
localized ponding in poor drainage areas. Additionally, model
soundings depicting tall, skinny CAPE allows for the potential
for some embedded thunder as the front moves through, though
higher coverage of storms is expected along and east of I-55
after daybreak.

Drier conditions are expected in the afternoon in the wake of
the front through Tuesday. Models are suggesting a weak 700 mb
wave moving across Iowa into lower southern Wisconsin late on
Monday. Given its projected track away from northern Illinois,
PoPs were kept dry and just something to monitor. Otherwise,
upper level ridging and surface high pressure will grow today
through Tuesday driving not just dry conditions but warm, above
normal temperatures. Lake breezes will help keep cooler
conditions cooler near the lake shoreline, but temperatures well
into the 80s can be expected farther inland.

Models are suggesting that by Wednesday morning, a near Omega
blocking pattern will set up in the mid-to-upper levels.
Ensembles are still suggesting that a weak 700 mb wave will move
northward from the Gulf to the mid Mississippi River Valley.
This could provide the next chances for rain and storms, but
models noticeably keep the better chances farther south
compared to 24 hours prior. As the stagnant pattern remains
toward the end of the week, conditions are looking dry and
seasonable beyond Thursday.

DK

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 1257 AM CDT Sun May 24 2026

Key aviation forecast messages:

- Period of SHRA with embedded TS expected early this morning
  at the Chicago area terminals.

- Associated IFR to LIFR CIGs expected with the SHRA, lowest
  near the lake, with IFR to near LIFR VSBYs.

While spotty showers will remain possible west of I-55 through
the rest of the overnight hours, expecting most areas to stay
dry through ~9Z. Thereafter model guidance has remained
consistent in a quick expansion of shower coverage into the
Chicago metro, though with slightly slower onset and end times.
Have accordingly shifted the timing by about an hour later for
most sites. While confidence in thunderstorm coverage is on the
lower side, isolated embedded non-severe thunderstorms will be
possible and have accordingly maintained TEMPOs for TSRA. Any
showers/storms that develop will also be efficient rain
producers with rainfall rates >=1"/hr possible. The increased
low-level moisture will also likely lead to quickly lowering
ceilings to IFR and potentially LIFR, lowest near the lakeshore
and under the heaviest showers. Showers and any isolated
embedded storms are expected to end from west to east from mid
morning through midday.

Light and variable winds are expected prior to the expansion of
shower coverage early this morning. Directions will settle into
a prevailing northwest direction in the wake of the
showers/storms initially with the potential for a weak lake
breeze turning winds east at the Chicago terminals during the
mid to late afternoon.

Similar to yesterday, given increased low-level moisture in the
wake of this morning`s showers and storms, we will have to
monitor fog and low ceiling trends over Lake Michigan into the
evening and early overnight hours in case it happens to ooze
inland again.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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